HONG KONG — A decade after severe acute respiratory syndrome, or SARS, swept through Hong Kong and then around the world, the city is among the first to become worried about the emergence and spread of another, genetically related virus in the Middle East.Medical researchers emphasize that they do not know if the new virus will develop the same ability as SARS to spread from person to person. The World Health Organization is taking a cautious stance.The health organization announced Tuesday that the virus, known as a coronavirus, had killed 11 of the 17 people infected so far, including a man in Britain who fell ill after traveling to Saudi Arabia and Pakistan. The health organization asked member governments to report any new cases, but it stopped short of urging any special measures.“W.H.O. does not advise special screening at points of entry with regard to this event, nor does it recommend that any travel or trade restrictions be applied,” the agency said.But Hong Kong is already taking preventive measures. Without a single confirmed human case of the new virus in East Asia so far, the government of the autonomous Chinese territory has already begun alerting and training employees at hospitals, clinics and the airport to identify possible cases. Wide-ranging medical research is already under way.Senior government officials held an extensive exercise on Wednesday to simulate the oversight of the quarantine and treatment of patients and their associates if a single person infected with the new virus arrived at the Hong Kong airport and began spreading it. The Health Department announced that it would “stay vigilant and continue to work closely with the W.H.O. and other overseas health authorities to monitor the latest development of this novel infectious disease.”No cases have been documented in the United States. In Europe, in addition to the death in Britain, a 73-year-old man died in Germany on Tuesday after being evacuated from the United Arab Emirates a week earlier.The Hong Kong government’s measures reflect a continued preoccupation with public health — some say an obsession — that came about after nearly 1,800 people in Hong Kong became extremely ill with SARS in a few weeks during the spring of 2003, with 299 of them dying.“At the moment, I think Hong Kong is likely to be the one with the strongest border control against this new virus for obvious historical reasons,” said Dr. Yuen Kwok-yung, chairman of the infectious diseases section of the microbiology department at Hong Kong University.Some health experts in the West have been wary of drawing too much attention to the new virus, a coronavirus like SARS. They point out that as researchers have begun looking harder for coronaviruses after the SARS outbreak, they have found more of them.Much of the research has been done in Hong Kong, which became a leading center for disease research as a British colony before the handover to China in 1997; the bacteria that causes bubonic plague was discovered in Hong Kong in 1894. The World Health Organization has long sent samples from all over Asia to Hong Kong University for testing, and Dr. Yuen and his colleagues at the university played a central role in identifying the SARS virus in 2003 and then tracing its genetic similarities to a virus that infects wild bats.Hong Kong University researchers are now expressing growing concern about the new coronavirus that has emerged in the Middle East, known as novel coronavirus. Dr. Malik Peiris, a co-discoverer of SARS who is the director of the center for influenza research at Hong Kong University, warned in a speech on Tuesday that while SARS faded away after a year, with 8,445 cases and 790 deaths worldwide, two other coronaviruses had jumped from animals to people in the past two centuries and become endemic.Both of those coronaviruses cause common colds. One of the concerns about the novel coronavirus is that it seems deadlier, having killed more than half of the people with confirmed cases. A study published this week in The Journal of Infectious Diseases by Dr. Yuen and 12 colleagues in Hong Kong and mainland China found that the new virus also infects a wider range of human tissue types than the SARS virus and kills them more quickly.The new virus also infects cells from a variety of animals, including monkeys, rabbits and pigs, which could offer further opportunities for the new virus to develop greater transmissibility in people. The virus appears genetically close but not identical to viruses found in wild bats in Asia and in Europe.One big question is whether far more people are being infected without detection, in which case the disease may kill a lower percentage of victims but also be more transmissible. Dr. Yuen said that when 2,400 people were screened recently in Saudi Arabia for antibodies to the virus, none had them.That suggests that the virus is periodically infecting people from an unknown animal host, but it has not developed the ability to pass easily from person to person, he said. However, the man in Britain who fell ill with the virus after traveling to Saudi Arabia and Pakistan infected two members of his household in Britain before he died of the disease. And one of them, with a pre-existing health problem, has also died.The H5N1 avian influenza virus has been periodically jumping from birds to people and causing sporadic deaths for 16 years without developing sustained transmissibility among people. On the other hand, the SARS virus appears to have developed transmissibility after only a few months of sporadic infections of people in southern China in late 2002.For the new virus, “we may be at the 2002 situation at this time, and that would be very, very bad,” Dr. Yuen said. “But this also may be like H5N1.”